The regularity of the seam existing between display tiles in a tiled display is important to avoid visual artefacts. The regularity of the seam is a function of the alignment of the display tile. Technique and apparatuses to align display tiles in tiled display are known in the art. For instance, U.S. Pat. No. 8,384,616B2 describes how clips and receptacles are used to align adjacent display tiles with a high accuracy.
These and similar tile alignment techniques suppose that the LED themselves are properly aligned with the tile itself.
The LEDs are soldered to a LED board and the LED board is fastened to a carrier board. Aligning the LED board and the carrier board is usually done by means of one or more reference pin(s). The reference pin(s) is/are used to align the LED board with references (e.g. a corner) of the carrier board. Unfortunately, there are tolerances on the position of the LEDs with respect to the LED board on which they are soldered and therefore, aligning the LED board perfectly with the carrier board by means of reference pins on the LED board does not mean that the LED themselves will be perfectly aligned with the carrier board. As a result, even if adjacent LED tiles are perfectly aligned, the relative position of the LEDs on different LED tiles may vary across a tiled display, thereby introducing visual artefacts.
Another problem not addressed by the clips and receptacles used in the prior art is the “z-coordinate” or position of the LED in a direction perpendicular to the plane of the LED board. Variation of the z position of the LED from tile to tile is the source of visual artefacts when the direction of a viewer's gaze is not along the normal to the plane of a tiled display.
What is needed is a solution to adjust the distance between the top of the LEDs on the LED board and a reference, e.g. the back surface of the carrier board.
It is known in the art to adjust the distance between two objects fastened together with e.g. screws and bolts by adding washers between the two objects. The problem with this technique is that varying the distance between two objects is only possible by multiples of the thickness of the washers if off-the shelf washers are used or that the washers have to be machined for every LED board in function of the actual distance between the LED and the LED board. This is neither practical nor economical.